1. Technical Field
The present invention relates to a black toner and an image forming method.
2. Related Art
An image forming apparatus employing an electrophotographic process, such as a printer, a duplicator and a facsimile machine, forms an image formed of a toner on a recording medium, such as paper, by a sequence of image forming process including charging, exposing, developing, transferring and fixing.
The image forming apparatus is equipped with a developing device having a developing roller having a toner supported thereon. The developing device has the developing roller that faces a photoreceptor drum having an electrostatic latent image, and the toner is applied to the photoreceptor drum from the developing roller, thereby visualizing (developing) the latent image on the photoreceptor drum as a toner image.
In general, a toner is electrically charged and then subjected to development. It is known that a charge controlling agent is used for charging the toner efficiently (as described, for example, in JP-A-2005-49489).
However, the known toner undergoes fluctuation in charging property among the toner particles, and even though a charge controlling agent is added, the fluctuation cannot be sufficiently suppressed, thereby providing a problem due to adverse effect on developing characteristics and transferring characteristics. In particular, a positively charged toner containing carbon black as a colorant significantly undergoes the problem, and thus, inversely charged particles cannot be suppressed from being formed to provide defects including fog and the like.